Company Profile

Doppler Flow Meters and Ultrasonic Trackers: Reliable Velocity Profiling for Slurries and Aerated Fluids

Quick Answer: Silver Instruments Doppler flow meters and ultrasonic trackers measure flow velocity in slurries and aerated fluids with repeatable results. They work best on full pipes with suspended solids above 100 mg/L or gas bubbles above 1 percent void fraction. Send us your pipe size (DN), solids content, aeration level, temperature (°C), pressure (bar) and flow range for a quote.

Where Doppler Flow Meters Work Best

Standard transit time ultrasonic meters struggle in fluids with solids or gas. The sound path breaks down when bubbles or particles scatter the signal. But Doppler meters use the opposite principle. They read frequency shifts from moving particles or bubbles. They are a practical choice for slurry and aerated fluid lines.

In practice, we have supplied Doppler meters for mining tailings in Chile, dredge lines in Indonesia, wastewater sludge in Australia, and paper stock in Vietnam. These are not clean water jobs. The pipe often carries 5 to 15 percent solids by weight. Standard inline meters clog or wear out. A clamp-on Doppler sensor has no wetted parts.

How Ultrasonic Trackers Profile Velocity on Aerated Lines

Doppler sensors transmit an ultrasonic beam into the pipe wall and the moving fluid. Particles or gas bubbles reflect part of that signal. The reflected frequency shifts in proportion to velocity. Silver Instruments trackers sample this shift hundreds of times per second. The transmitter converts the result into a flow reading.

Here is the thing. Aerated fluids are not a problem if the bubble density is high enough to reflect the signal. Too little aeration gives weak return. Too much foam can attenuate the beam. Most engineers skip this part during pilot tests. You should record the aeration level at the intended sensor location. Then we can check the signal strength before quoting.

Key Selection Parameters

Send us these details and we can recommend the right model.

Pipe size from DN25 to DN3000. Doppler clamps on metal or plastic pipes. Wall thickness matters above 20 mm. For DN15 lines, choose an oval gear flow meter or a Coriolis mass flow meter instead.

Fluid type and solids content in mg/L or percent by weight. Typical lower limit is 100 mg/L for fine particles.

Aeration level in percent void fraction. Target range is 1 to 10 percent for reliable Doppler return.

Temperature and pressure at the sensor point. Standard transducers handle 80 °C. High temperature versions handle 150 °C.

Outputs such as 4-20 mA, HART, RS485 Modbus, pulse or relay. We also integrate PT100 inputs for energy monitoring on selected skids.

Doppler meters show velocity and volumetric flow. They do not directly compute mass flow in kg/h unless you enter density. We can integrate a density input or use a Coriolis mass flow meter for that job. Viscosity in cP and conductivity in µS/cm are not critical for Doppler sizing.

Model Pairing for Common Applications

For permanent mounting on slurry pipelines, Silver Instruments DFM series clamp-on Doppler flow meters are a direct fit. The sensor bolts to the outside of the pipe with stainless steel straps. No cutting and no flange work. You do not need a shutdown.

For field surveys and pump audits, our portable ultrasonic tracker works well. Users move the sensor from one station to the next. It stores measurement points in internal memory and exports through USB or RS485.

For clean liquid lines without enough solids or bubbles, use a separate transit time ultrasonic flow meter. We stock both types. Tell us the fluid condition and we will not sell you the wrong sensor.

Installation Notes That Prevent Bad Readings

One common error is mounting a Doppler sensor